British Geological Survey, Environmental Science Centre, Nicker Hill, Keyworth, Nottingham NG12 5GG, UKCentre for Environmental Geochemistry, School of Geography, University of Nottingham, University Park, Nottingham NG7 2RD, UK
Map showing the location of North Sea study site well 22/10a-4 and other sites described in this study in relation to the main Mesozoic structural elements and distribution of Tertiary sediments and volcanics (modified from several maps from King, 2016).
Palaeocene–Lower Eocene stratigraphy of the North Sea and Faroe-Shetland basins compared to southern England (modified from Huggett & Knox, 2006; Mudge, 2015). Pyroclastic phases 1 and 2 from Knox & Morton (1988). T-M = tectonic-magmatic phase. Tectonic events: A = short-lived regional uplift; B = regional plume-induced uplift; C = uplift of Scottish source areas; D = regional uplift (N. Atlantic thermal updoming); E = onset of NE Atlantic sea-floor spreading and regional thermal subsidence; F = regional uplift.
Lithological, gamma-ray and sonic wireline geophysical logs and low-resolution sediment core clay mineralogy for well 22/10a-4 plotted against logging depth (modified from Knox, 1996; Huggett & Knox, 2006). Huggett & Knox (2006) later identified the Sele Formation 1a/1b unit boundary at 2609.5 m (core depth). Kender et al. (2012) identified the carbon isotope excursion (CIE) of the PETM, and raised the Lista/Sele formation boundary to 2630.5 m (core depth). With the exception of this figure, all sample depths used in this study are core depths.
Comparison of a composite modelled XRD profile with an experimental ethylene glycol-solvated XRD trace; sample depth 2612.35 m, Sele Formation Unit 1a (upper figure). Modelled XRD traces for each clay mineral component (illite-smectite, illite, kaolinite and chlorite) with peak positions (Å) are shown in the lower four figures. Note the different intensity scales for the component traces.
Downhole distribution of clay minerals for the 22/10a-4 samples as a proportion of the <4 µm fraction, compared to the carbon isotope measurements on total organic carbon (TOC) (from Kender et al., 2012).
Sample XRD traces (air-dry, ethylene glycol-solvated and heated 550°C) to illustrate the clay mineral assemblages identified in the 22/10-a4 samples: (a) Lista Formation, 2651.46 m; (b) Sele Formation Unit 1a base and middle, 2624.51 m; (c) Sele Formation Unit 1a upper, 2612.84 m; and (d) Sele Formation Unit 1b, 2608.20 m.
Downhole variation in clay mineral indices for the 22/10a-4 samples: K/(I-S) and K-I and %‘sand’ compared to total organic carbon (TOC) isotopic and micropalaeontological proxies from the same core (from Kender et al., 2012). The carbon isotope excursion (CIE) can be correlated to the global CIE of the PETM.
Comparison of kaolinite (this study) and sediment carbon isotope (from Kender et al., 2012) from 22/10a-4 with recent studies from Arctic Spitsbergen (Harding et al., 2011), New Jersey Margin (John et al., 2012) and the Eastern North Atlantic (Bornemann et al., 2014).